5-earthmass planet found

[Martin]

Most exoplanets found so far are far more massive than earth (Jupiter-size). And many have close-in orbits presumably making them hot.

 

So it's interesting there is a report of detecting an exoplanet that not only is NOT close-in----it is between Mars and Jupiter distance from its star----but also is a modest 5.5 earth masses.

 

http://dabacon.org/pontiff/?p=1176

http://www.nature.com/news/2006/060123/full/060123-5.html

 

NATURE says:

25 January 2006

Found: one Earth-like planet

Astronomers use gravity lensing to spot homely planets.

Mark Peplow

 

Astronomers say they have found the most Earth-like planet yet outside our Solar System. At just 5.5 times the mass of Earth it is one of the smallest extrasolar planets ever found, and orbits its star at a distance comparable to that of habitable worlds.

 

Similarly sized extrasolar planets have been found before. But the method used to detect them meant we could see smallish planets only when they were very close to their suns, and such bodies are battered by scorching radiation.

 

Planet OGLE-2005-BLG-390Lb looks much more like home. It lies about 390 million kilometres from its star: if it were inside our Solar System, the planet would sit between Mars and Jupiter...

[Martin]

BBC article here:

http://news.bbc.co.uk/2/hi/science/nature/4647142.stm

 

How they found this planet is pretty interesting. they used gravitational lensing

 

Clear explanation of technique here:

http://cosmicvariance.com/2006/01/25/general-relativity-as-a-tool/

 

 

More blog discussion of gravitational lensing technique for exoplanet search came up here:

http://scienceblogs.com/principles/2006/01/a_new_life_awaits_you_in_the_o.php

 

 

For completeness here is the Nature link from

preceding post.

http://www.nature.com/news/2006/060123/full/060123-5.html

[Martin]

By far the best blog report of this I've found so far is by

Anthony Kendall

 

http://www.anthonares.net/2006/01/published-research-synopsis-55-earth.html

 

the mass is uncertain, 5.5 is only an average or most likely value

 

Anthony gives the LIGHTCURVE that they observed

over the course of half a day, the planet passed behind or in front of the star and so it contributed some extra mass to the lensing effect causing a BLIP

 

light from a more distant star was brightened more, by the stronger lensing, during that half a day. the plot of the light curve shows this blip. it is superimposed on a 40-day lightcurve that represents the lensing star passing in front of the more distant star..

 

If I'd known about Anthony's report earlier I might have just linked to that and skipped the BBC, Nature, etc. He's thorough and clear.

 

the light curve is really neat. it plots the variation of the distant star brightness over FORTY DAYS as the nearer star passed in front (between us and it) with the days numbered -20 to +20------and around day +10 there is this little blip lasting about half a day, caused by the PLANET lining up and contributing a slight extra lensing

 

 

Another thing Anthony has is a plot of EXOPLANETS discovered so far arranged by MASS AND ORBIT DISTANCE. So you can see that there have been some already discovered with this low mass, but they were much closer in to the star. And the plot shows the bulk of those found had much larger mass. The graphing is logarithmic

 

Great science.

the technical journal article, which I havent seen yet, is

Beaulieu, J.-P. and 72 others (2006). Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing. Nature 439(7075), pp. 437-440.

 

If I can find it online I will post a link.

 

UPDATE:

Whoa! there is a preprint of the Beaulieu article on ARXIV

 

http://arxiv.org/abs/astro-ph/0601563

[AzurePhoenix]

I wonder what kinda atmosphere could something that size likely have?

[Martin]

I wonder what kinda atmosphere could something that size likely have?

 

put it around a star like the sun, and the question makes sense

 

the trouble with this particular case is that the star they happened to observe the planet around is a LOW MASS star (only about 1/4 the mass of the sun) and these make dim light---they are low-wattage stars.

so this particular planet is dreadfully cold

 

the usually abundant gasses would have all condensed to liquid or even turned solid

 

it is almost not even worth trying to imagine or speculate----little is known and that little is pretty dismal

 

the news excites me because it means they will start using this technique more and finding more planets like this, and some will doubtless be around stars more like the sun in mass. what I like is not this planet itself but the sophisticated way of seeing it----gravitational lensing spikes in the lightcurve

[AzurePhoenix]

the news excites me because it means they will start using this technique more and finding more planets like this' date=' and some will doubtless be around stars more like the sun in mass. what I like is not this planet itself but the sophisticated way of seeing it----gravitational lensing spikes in the lightcurve[/quote'] I'm just obsessed with new types of worlds, different landscapes and such, and often lose sight of just how limited even the most exciting methods tend to be. Well, let us look forward to the time when technology will sate both our desires.

[Martin]

I'm just obsessed with new types of worlds, different landscapes and such, and often lose sight of just how limited even the most exciting methods tend to be. Well, let us look forward to the time when technology will sate both our desires.

 

if you want to feed your imagination then icy planets like this are OK if you can imagine clean-safe nuclear power (or some geothermal alternative)

 

a civilization could live on a cold planet UNDER THE ICE if they had a source of heat and light

 

the ice would be an insulating shield and a kind of self-sealing protection

 

so one can picture some Jupiter moon like Callisto or Europa which has a tidal-heated core but is very cold on the outside, and the inhabitants melt a bubble to live in deep in the ice. If it's big enough they can even have some ponds and lakes of (rather chilly) water down there

 

the main thing is having plenty of energy for light, so you can grow appletrees and veggies and basically have a life.

 

the drawback to this recent iceball is that if the mass estimate of 5.5 is right then it is likely uncomfortable even in a nice environment

 

the moon is 1/80 the mass of the earth. Anything from one percent of mass of earth up to 100 percent seems like something I could cope with.

 

But 500 percent earthmass is just too much gravity for the likes of us.

 

approve your obsession with visualizing exoplanets. in a few years we should have found one with specs permitting familiar temperature and atmospheric pressure

[RyanJ]

Interesting article, thanks for sharing!

 

Cheers,

 

Ryan Jones

[MindOfChaos]

175% earth mass mite be bearable after you adjust and build more muscle to handle the weight. You would not be able to run that fast and you would probably end up becoming short and stocky bacause of the weight. 550% earth mass on the other hand i think that is to much g forces to deal with. You would weigh 5.5 times what you do on earth. As for 1% of earths gravity im not so sure about that idea either. Your mucles would get weaker with out the need for them to work as much and your bones would become thinner. Just like you hear about with past prolonged space missions on places like the Mir space station. Also trying to goto the Loo in such low gravity enviroments doesn't sound fun either.

 

As with imaging other planets its something i used to do when I was a kid. More recently I try and imagen other types of thoughts or intellegences. Even trying to understand every differen't view point of humans is enough of a challenge for me.

 

Other planets will become much more interesting when we have some way to actually travel there. Like some sort of hyperspace technology or something.

I hope some thing like that may develop within my life time. Probably not but it would be cool if it did.

[AzurePhoenix]

175% earth mass mite be bearable after you adjust and build more muscle to handle the weight. You would not be able to run that fast and you would probably end up becoming short and stocky bacause of the weight.

Our spines would sure as hell go out alot sooner.

[Specusci]

It sounds to me that everyone is basing the life off of "us" and "if we where/did this...". Isn't there a possibility that life could evolve to cope with the gravity, pretty much anywhere, so long as the life could evolve there in the first place?

[Martin]

...Isn't there a possibility that life could evolve to cope with the gravity, pretty much anywhere, so long as the life could evolve there in the first place?

 

Yes of course there is that possibility, Specusci. No one in this thread has said that there is no possibility of some other forms of life adapting to stronger gravity.

 

Talking about other forms of life is a separate issue, from the issue of what conditions on a planet would seem like to you or me, and whether WE or other earth creatures could somehow adapt.

 

===============================

 

Actually what interests me at this point is the techniques for detecting exoplanets and how people estimate conditions on those planets----like temperature and rough estimates of the surface gravity.

 

that's just my own personal viewpoint. I am personally less interested in speculating about other life-forms and more interested in the techniques by which we might identify earth-like planets and study them

 

and I mean with or without life. Planets are interesting to study in their own right, whether or not you imagine them evolving some local life-forms.

[JohnB]

Martin, I'm a tyro in this area but it seems to me that virtually all of our current detection techniques only detect worlds whose ecliptic plane includes Earth.

 

In this case, we see the planet when it passes in front of behind it's sun, in others when the star is seen to wobble from side to side.

 

Could we detect a more circular motion of a star indicitive of planets when we are looking at the star's "North Pole"? Could we detect planets near Alpha Centauri if we were looking "down" on the system rather than "across" at it?

 

If not; Then given that we have found planets in over 100 systems and that we can only find planets if their ecliptic plane includes Earth and that we can only detect them if we are looking at the right time.

 

Wouldn't this imply that planets are really quite common?

[Martin]

...current detection techniques only detect worlds whose ecliptic plane includes Earth.

 

...

Wouldn't this imply that planets are really quite common?

 

Without being an expert myself either, I can agree with you that your thinking is basically right.

 

we can infer that there are a lot more exoplanets than what we can see so far---and one way to see that is to say what you did----the techniques are most sensitive to orbits viewed edge-on or nearly edge on

 

the WOBBLE that they detect is actually not SIDE-TO-SIDE but towards/away

 

it is interesting, they measure the towards/away DOPPLER of the star which could be just a few tens of meters per second

 

nevertheless to see the towards/away (or "radial") speed of the wobble the plane of the motion has to not be tilted too much. 45 degrees tilt and we might still detect it. but 90 degrees tilt, as you imagined in your post, where we are looking DOWN on the system-----why then there isnt going to be any towards/away motion at all and nothing for us to detect!

 

A. people are going to be measuring star positions more and more accurately. I think they will get to where they can see wobble even looking down on the system. the present situation won't last forever

 

B. even with the present situation it is possible to allow for the limitations and estimate (as you did in post) the real abundance of exoplanets judging from the amount we can already see

==================

 

if you want links to online technical reading material about anything you can ASK if you want and say what level you prefer or just accept whatever comes along.

If you ask, then people when they are not too busy MAY reply with useful online references.

 

Like, even though I am not very knowledgeable I could still probably dig up some online stuff on detecting exoplanets.

 

so you can always start a thread, if something particularly interests you, and see what the board-group comes up with.

[JohnB]

Thanks mate. I'll go and have a dig around and see what I find.

 

As an aside. I remember reading years ago that another part of the search is to find oxygen absorbtion lines in stellar spectra. The first assumption was that O2 would not be in the sun so must be in the atmosphere of a world in front of the sun. The second assumption was that since O2 is a volatile gas, the only way it could exist in a planetary atmosphere was if it was being constantly refreshed. Hence photosynthetic life must exist.

 

I'd totally forgotten about it until this thread. Oh well, another search ahead of me.

[alext87]

Does anybody know of a exoplanet that is potentially habitable (Earth-like) that has been detected using the doppler method (wobble method) and the transit method?

[Spyman]

the drawback to this recent iceball is that if the mass estimate of 5.5 is right then it is likely uncomfortable even in a nice environment

 

the moon is 1/80 the mass of the earth. Anything from one percent of mass of earth up to 100 percent seems like something I could cope with.

 

But 500 percent earthmass is just too much gravity for the likes of us.

Wouldn't that depend on the density of the planet ?

 

The Moon has 1/80 the mass of Earth but you would weight 1/6 of your weight there.

 

Uranus have ~16 times more mass than Earth but your weight there would only be ~90 percent of on Earth.

http://www.exploratorium.edu/ronh/weight/index.html

 

 

Some astronomers have speculated that it may have a rocky core like Earth, with a thin atmosphere.

http://en.wikipedia.org/wiki/OGLE-2005-BLG-390Lb

 

If OGLE-2005-BLG-390Lb has the same average mean density as Earth, I calculate an increase in weight of 176 percent from Earth gravity. Of course higher mass would indicate higher density as well, (more gravity to compress matter), but we don't know the composition of it, so it's only one estimate...

 

That would mean a human with the weight 80 kg on Earth would weight around 141 kg there !

 

I guess that would be "uncomfortable" but not totally impossible to overcome.

 

Do you have rough estimates of the surface gravity by professionals when you say "too much" ?

 

 

Anyway this is what I wanted to post, apperently there is a new way to detect small exoplanets:

 

Imaging Earth-like exoplanets is a daunting challenge because the dim starlight that such relatively small worlds reflect is easily overpowered by the glare of their far larger, brighter parent stars. Now two astrophysicists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., have devised new techniques that can overcome this glare, enabling future space telescopes to snap pictures of Earth-like exoplanets up to 10 billion times fainter than the stars they orbit.

http://www.space.com/businesstechnology/070418_tech_wednesday.html

 

EDIT: This thread is in "Politics" ???

[Spyman]

Thanks, for moving this thread to a more appropriately place, Martin !

 

Any comments of my estimate of surface gravity...

[Martin]

Thanks, for moving this thread to a more appropriately place, Martin !

 

Any comments of my estimate of surface gravity...

 

I think you are probably right, Spyman.

 

BTW I don't know about moving the thread. The Admins do that. I didnt know that it wandered over in another forum for a while.

 

I think I was wrong initially suggesting the gravity would be difficult. If it is the same density as earth, then the radius would be greater by cuberoot5

and the surface gravity would be greater by only a factor of 5/(square of cuberoot5) = cuberoot5 = 1.7

 

So if the planet mass is 5 x earth, then you only feel 70 percent heavier.

 

I'm not being precise, but the idea is roughly what you say.

[bascule]

Similar story: a planet 50% larger than earth and warm enough to have liquid water has been discovered:

 

http://story.malaysiasun.com/index.php/ct/9/cid/b8de8e630faf3631/id/243780/cs/1/

[Martin]

Good find, Bascule!

 

Malaysia Sun seems to have gotten a scoop. reporting on 23 April but

a French newspaper reported it 24 April

http://www.france24.com/france24Public/en/news/world/20070422-Astronomy-red-dwarf-mother-earth.html

 

this is a significant discovery because there are likely to be a lot of these.

 

it is apt to be warm and wet

huddled close to its milder sun.

[Spyman]

5 times the mass of Earth and 1.5 times larger gives ~2.2 times stronger surface gravity, so an astronaut who weights 80 kg on Earth would roughly weight 176 kg down there.

 

Very intriguing find indeed, sparks my fantasy in several directions !

 

How old is Gliese 581 and whats the expected lifetime ?

 

 

"We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius, and water would thus be liquid," explains Stéphane Udry, from the Geneva Observatory (Switzerland) and lead-author of the paper reporting the result. "Moreover, its radius should be only 1.5 times the Earth’s radius, and models predict that the planet should be either rocky – like our Earth – or covered with oceans," he adds.

 

The host star, Gliese 581, is among the 100 closest stars to us, located only 20.5 light-years away in the constellation Libra ("the Scales").

http://www.eurekalert.org/pub_releases/2007-04/eso-aff042307.php

 

Seth Shostak, a senior astronomer at the SETI institute, said the Gliese 581 system has in fact been looked at twice before for signs of intelligent life. The first time was in 1995 using the Parks Radio Telescope in Australia; the second time occured in 1997 using the Greenbank Radio Telescope in West Virgina. Both times revealed nothing.

http://www.space.com/scienceastronomy/070424_hab_exoplanet.html

 

David Spergel, chairman of Princeton astrophysics department, noted in a telephone interview that the new planet, if it is indeed rocky, must be "tidally locked" to its sun the way our moon is to the Earth -- which means that it must always show its same face to its sun, and that while one side would be too fiercely hot to support life, the other side would be too cold.

 

But at the terminator -- the margin between the hottest and coldest parts of the planet -- Spergel agreed that liquid water could well exist, hurricane force winds would blow, and although the planet would be "radically different" from Earth, life might well exist in that difficult environment. "This is a big, impressive step," Spergel said.

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/24/BAG33PE14U26.DTL

 

But he and other astronomers cautioned that it was far too soon to conclude that liquid water was there without more observations. Sara Seager, a planet expert at the Massachusetts Institute of Technology said, “For example, if the planet had an atmosphere more massive than Venus’s, then the surface would likely be too hot for liquid water.”

 

“It’s 20 light years. We can go there,” said Dimitar Sasselov, of the Harvard-Smithsonian Center for Astrophysics, who studies the structure and formation of planets.

http://www.nytimes.com/2007/04/25/science/space/25planetcnd.html?_r=2&oref=slogin&oref=slogin

 

The idea that other, less-massive, dimmer stars than the Sun could also host habitable worlds has long been debated. A particular class, M-Stars, are of interest simply because there are so many of them—they are the most common star in the galaxy. They’re the cool stars that inhabit our neighborhood.

 

There’s considerable interest in the question of whether M-Stars could host habitable planets. Would the planets be tidally locked with one face always directed toward the M-Star? Would flares wipe out life on the local planet? If M-Stars could host habitable planets, life may be much more widespread that we’ve previously thought. Thus, M-Stars are of interest to astrobiologists including SETI scientists who are searching for life beyond Earth.

 

“One…aspect of M dwarfs makes them intriguing for SETI: they may be ideal hosts for advanced technological civilizations because they live an extraordinarily long time. Stars like the Sun live (i.e., they fuse hydrogen into helium) for only about 10 billion years. No M dwarf that ever formed has yet to die; no M dwarf will die for more than another 100 billion years. With such long lifetimes, there are big possibilities for these small stars.”

http://www.space.com/searchforlife/070412_seti_thursday.html

[Comandante]

Was it determined at what speed this planet rotates on its own axis? In either case, would this have any implications on possibility or sustainability of life? My guess would be 'not much' but just curious.

[immortal]

Another interesting discovery two planets host to a binary system called CM Draconis having strong evidence for alien life.

 

Links

http://www.virtuallystrange.net/ufo/updates/2001/jan/m07-017.shtml

http://www.wired.com/science/discoveries/news/2001/02/41483?currentPage=all

[Spyman]

How old is Gliese 581 and whats the expected lifetime ?

Gliese 581 is a cool and dim, main sequence red dwarf (M2.5 V). The star has almost a third (31 +/- 2 percent) of Sol's mass, possibly 29 percent of its diameter, and a bit more than one percent (around 0.013) of its visual luminosity. The star appears to be only around 47 to 56 percent as enriched as Sol in elements heavier than hydrogen ("metals").Its kinematic characterisitcs, magnetic activity, and sub-Solar metallicity indicate that that Gliese 581 is at least two billion years old.

http://www.solstation.com/stars/gl581.htm

 

According to The Extrasolar Planets Encyclopaedia: Gliese 581 is ~4.3 Giga years old.

http://vo.obspm.fr/exoplanetes/encyclo/star.php?st=Gl+581

 

Animation of the planetary and potentially habitable zone orbits: http://www.solstation.com/orbits/gl581sys.htm

 

Red dwarfs fuse hydrogen to helium via the proton-proton (PP) chain. Due to the low temperatures in the core, fusion proceeds slowly. Consequently they emit little light, sometimes as little as 1/10,000th that of the sun. In general red dwarfs transport energy from the core to the surface via convection. As red dwarfs are fully convective, they can burn a larger proportion of their hydrogen before leaving the main sequence than larger stars, such as the Sun. Thus red dwarfs have an enormous estimated lifespan; from tens of billions up to trillions of years depending upon mass; the lower the mass, the longer the lifespan.

http://en.wikipedia.org/wiki/Red_dwarf

 

What happens after a low-mass star ceases to produce energy through fusion is not directly known: the universe is thought to be around 13.7 billion years old, which is less time (by several orders of magnitude, in some cases) than it takes for the fusion to cease in such stars. Current theory is based on computer modelling.

 

A star of less than about 0.5 solar mass will never be able to fuse helium even after the core ceases hydrogen fusion. There simply is not a stellar envelope massive enough to bear down enough pressure on the core. These are the red dwarfs, such as Proxima Centauri, some of which will live thousands of times longer than the Sun. Recent astrophysical models suggest that red dwarfs of 0.1 solar masses may stay on the main sequence for almost six trillion years, and take several hundred billion more to slowly collapse into a white dwarf.

http://en.wikipedia.org/wiki/Stellar_evolution